A number of different types of railroad cars are available, particularly categorized according to the type of cargo for which they are intended. The type of cargo dictates a number of requirements such as cubic foot capacity, floor strength, side wall strength, covered or uncovered, and so forth.
Gondola cars are typically open or uncovered vehicles and are used to carry a large variety of industrial cargo. But even within the category of gondola railcars, several different types are available, again depending upon the type of cargo to be handled. Specifically, some gondola cars are designed to carry wood chips and similar products of relatively low density, while other gondola cars carry such products as coal which is of relatively higher density. So called “mill” gondola cars are commonly used around steel mills and are intended for carrying such cargos as steel scrap, slag, or steel sheet. With regard to steel sheet, quite often the sheet may be wider than the gondola car, and would therefore be loaded into the gondola car diagonally, i.e., extending from one lower corner of the car to the opposite upper corner of the car. Mill gondola cars, therefore, require a very high lateral load strength. Because of the types of loads carried and the manner of unloading cars such as with clam shell buckets or magnets, most cars cannot have any interior bracing.
Experience has shown that mill gondola cars are subject to extreme abuse, with most typical structural failures occurring at the connection of the side to the underframe at the side post interface. Analysis of various car constructions has confirmed that the connection of the side post and the underframe is one of the most critical areas of the car.
Typically such gondola cars are constructed in stages wherein the subframe and floor assembly is first made and the side assembly is separately made. The side assembly includes a number of vertical channel or hatshaped posts for reinforcing the side, and these assemblies are attached to the subframe assembly, with the side posts being either bolted or welded to the subframe assembly. Because typically no internal lateral reinforcement is used in a mill gondola car, lateral loads on the side walls of the car tend to tear the side posts away from the subframe assembly.
Gondola cars carrying less dense materials are often flood loaded from the top and unloaded by rotating the car and dumping from the top. There is a demand to transport commodities such as low density scrap and demolition material in cars without interior bracing so they can be loaded and unloaded similar to mill gondolas. The loading/unloading buckets impact the car bodies much like mill gondolas causing substantial damage. Also, the cars are typically longer and higher because of the lower density commodity.
Because internal bracing is disfavored in these type of cars, the lateral loads have to be transferred down the posts into the underframe. These loads include lateral unloading/loading impacts.
Accordingly, there is a need to develop a better moment connection between the posts and the underframe.